| Octet No. | Contents |
|---|---|
| 12-15 |
Reference value (R) (IEEE 32-bit floating-point value) |
| 16-17 |
Binary scale factor (E) |
| 18-19 |
Decimal scale factor (D) |
| 20 | Number of bits used for each packed value |
| 21-24 | Pre-processing parameter (B) (IEEE 32-bit floating-point value) |
| Notes: (1) The template is approriately designed for data sets with all non-negative values and a wide variability range (more then 5 orders of magnitude). It must not be used for data sets with negative values or smaller variability range. (2) A logarithm pre-processing algorithm is used to fit the variability range into one or two order of magnitudes before using the simple packing algorithm. It requires a parameter (B) to assure that all values passed to the logarithm function are positive. Thus scaled values are Z=ln (Y+B), where Y are the original values, ln is the natural logarithm (or Napierian) function and B is chosen so that Y+B>0. (3) Best pratice follows for choosing the B pre-processing parameter. (a) If the data set minimum value is positive, B can be safely put to zero. (b) If the data set minimum is zero, all values must be scaled to become greater than zero and B can be equal to the minimum positive value in the data set. (4) Data shall be packed using Data template 7. |